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Homework Help: Energy to put space shuttle in orbit

  1. Apr 7, 2009 #1
    1. The problem statement, all variables and given/known data
    The space shuttle orbits about 300km above the surface of the Earth. The shape of the orbit is circular and the mass of the space shuttle is 6.8*104kg. The mass of the earth is 6.0*1024kg and the radius of the earth is 6.4 *106m. Calculate the energy needed to put the space shuttle into orbit.

    2. Relevant equations


    3. The attempt at a solution
    Using G=6.67*10-11 with the mass of the earth and shuttle and the radius of the earth gives 4.2*1012J but the answer should be 2.2*1012J according to the book. Where am I going wrong?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Apr 7, 2009 #2


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    Staff Emeritus
    Science Advisor

    Think about what the gravitational potential energy GMm/r means.

    The shuttle lifts (or rises) from re to re+300 km, where re is the radius of the earth.
  4. Apr 7, 2009 #3


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    Science Advisor
    Homework Helper


    Hi calculator20! :smile:
    erm :redface: … you can't just leave it there :rolleyes: … it'll crash! :eek:

    try giving it a shove! :smile:
  5. Apr 7, 2009 #4
    If I do GMm/re I get 4.2*10 to the 12, GMm/re + 300000 gives 4.06 * 10 to the 12. The difference between them isn't 2.2 *10 to the 12?
    I get
  6. Apr 12, 2009 #5
    i am having exactly the same difficulty, its frustrating the hell out of me.
    either i am not seeing something or there is an error in the answer page
  7. Apr 12, 2009 #6


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    Homework Helper

    Welcome to PF.

    They want the total energy.

    What is total energy to move from the surface of Terra to a 300km height?

    What must the object have to be in orbit?

    Etotal = ΔKE + ΔPE
  8. Apr 12, 2009 #7
    so basically 2.2= KE (4.2) - PE (2.1)
    allowing for roundings

    Thanks a lot x
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